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Subject: Re: [PATCH V2] slub: avoid potential NULL dereference or corruption
From: Pekka Enberg <penberg@kernel.org>
To: Christoph Lameter <cl@linux.com>
Cc: Eric Dumazet <eric.dumazet@gmail.com>,
        linux-kernel <linux-kernel@vger.kernel.org>,
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Date: Wed, 23 Nov 2011 23:19:51 +0200
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On Wed, 2011-11-23 at 09:17 -0600, Christoph Lameter wrote:
> On Wed, 23 Nov 2011, Pekka Enberg wrote:
> 
> > On Tue, 22 Nov 2011, Eric Dumazet wrote:
> > > show_slab_objects() can trigger NULL dereferences or memory corruption.
> > >
> > > Another cpu can change its c->page to NULL or c->node to NUMA_NO_NODE
> > > while we use them.
> > >
> > > Use ACCESS_ONCE(c->page) and ACCESS_ONCE(c->node) to make sure this
> > > cannot happen.
> > >
> > > Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
> >
> > Did someone test this patch? Does it fix any of the reported issues?
> 
> It does not fix any current issues but it is safe against potential
> compiler refetching of variables that we have already checked against
> bad values.
> 
> I thought I acked it already?

Yes, you did. I'm just trying to figure out which ones are going
straight to Linus and which ones can wait for v3.3.

			Pekka